An Arapahoe High School security guard claims he was the person who confronted Karl Pierson moments before the armed student shot himself inside the school's library last month. He also believes the incident might have been avoided if administrators had responded to warning signs appropriately.

Cameron Rust is an Arapahoe High football and baseball coach and also a security guard at the school. Thursday he posted a lengthy letter on his wife's Facebook page titled "Why This Did Not Have to Happen, I Know, I Was There." The letter was first noticed by KUSA 9 News in Colorado.